The object of the invention is a process for admixing fuel gas with the combustion air in an internal combustion engine in which ambient air is introduced into the cylinder head of the engine through a feed pipe and is enriched with fuel gas before introduction into the piston chamber, and wherein the fuel gas is introduced into the feed pipe counter to the flow direction of the combustion air. The object of the invention is furthermore a device for admixing fuel gas with the combustion air in an internal combustion engine, having a feed pipe for combustion air sucked in from the surroundings and having at least one injection nozzle for fuel gas, wherein the injection nozzle is installed counter to the flow direction of the combustion air in the feed pipe.
It has been known for many years, in particular, to operate stationary motors of heat coupling facilities with natural gas. There are also already motor vehicles in operation which are driven by natural gas. The operation of stationary internal combustion engines with natural gas is comparatively unproblematic, because sufficient time is available for an optimal adjustment of the parameters, and once the optimal setting has been reached, it delivers constant values for a long time. The situation appears otherwise with vehicle motors with changing load operation. Most known gas-driven engines are driven in dual fuel operation, that is, natural gas as well as gasoline can be used for operation. Such dual fuel engines fail by far to meet current and future requirements of air quality regulations.
The reason for poor exhaust gas values lies especially in the composition of the natural gas. The natural gas has a quite different chemical composition depending on its origin. The composition can also change within very short intervals of time even with the same origin. The major European distributor organizations for natural gas, which supply their product into the connection conduits of the individual states, admix additional components with the gases arriving from their countries of origin, which accumulate elsewhere as by-products. These are butanes, propanes and/or others.
The standards which are imposed on an admixture of natural gas in combustion air, i.e., air sucked in from the surroundings, necessary for combustion in the motor, are numerous and must be capable of continuous adaptation during the operation of the motor independently of its load status. Consequently, exact maintenance of a stoichiometric proportion does not by itself suffice for attaining a clean, exhaust-gas poor combustion.
In contrast to liquified gases used in a pure state, such as butane and propane, which are already in use in many places for the operation of vehicles, especially for stacker trucks and street cleaning vehicles, a trouble-free admixture of natural gas with combustion air is extremely difficult. Problems also arise, among other reasons, on account of the various densities of the components contained in natural gas. If the admixture of fuel gas/air has not already taken place without difficulty prior to introduction into the piston chamber of the internal combustion engine, then no combustion can take place there, which results in poor exhaust gas values. Without a trouble-free combustion, the use, and especially the expenditure for the use, of natural gas as a fuel for motor vehicles is not justified.
In contrast to the liquified gasses and even to liquid fuels, such as benzene and diesel fuel, additional higher investments are necessary for the storage of natural gas. This namely can only be transported and stored under high pressure or at very low temperatures in the liquid state. This means that not only at gas stations, but also especially in the vehicle as well, the natural gas must be stored in a pressure reservoir. Likewise, pressure lines and/or compressors for liquefaction or cooling tanks for a cooling to minus 176.degree. C. must be continuously available in the entire natural gas transportation chain.
A gas-air admixture device for an internal combustion engine is known from JP-A-61070161, to which the fuel gas is fed in a direction counter to the flow direction of the combustion air and is distributed in the combustion air by means of a conical valve.
Furthermore, a fuel gas feed with a valve, which feeds the fuel gas in a direction counter to the flow direction of the combustion air flow direction, is known from JP-A-60233359. No fuel/air mixture adapted to the number of cylinders to be charged with fuel gas can be generated with the two known devices.